As is disclosed in Patent Document 1 and other known documents, a hybrid vehicle is widely known, which has, as a vehicle drive system, an engine, a transmission, a motor (usually, motor/generator) interposed between the engine and the transmission and a clutch interposed between the motor and the engine to operatively connect and disconnect these motor and engine.
In Patent Document 1, there is disclosed a rapid deceleration control that is carried out in such hybrid vehicle. In the control, deceleration of the vehicle is detected and when the detected deceleration is rapid deceleration exceeding a predetermined value, the clutch between the motor and the engine is disengaged thereby to release the engine from the motor and thus from drive road wheels. That is, by disengaging the clutch in advance based on the deceleration of the vehicle, undesired engine stall caused by an excessive engine speed reduction resulting from the vehicle speed reduction is suppressed.
However, in the above-mentioned control in which only disengagement of the clutch is carried out upon the rapid deceleration of the vehicle, it tends to occur that the disengagement of the clutch through a hydraulic pressure is somewhat delayed depending on the condition and in such case, the engine speed is brought to a resonant speed (viz., an engine speed that causes a resonance of a vibration system including an engine mount) thereby to increase the possibility of vibration of a floor of the vehicle body.